Aluminum production from alloy



Sept. 3, 1963 G. MESSNER 0 ALUMINUM PRODUCTION FROM ALLOY 7 Filed April 18, 1960 3 Sheets-Sheet 1 FI-F'FFFFI-FFFFMR INVENTOR. CEORG MESSNER Hitorneys Se t. 3, 1963 Filed April 18, 1960 G. MESSNER f ALUMINUM PRODUCTION FROM ALLOY 3 Sheets-Sheet 2 INVENTOR.

GEORG MESNER Mwyw lqtiorneys Sept. 3, 1963 G. MESSNER 3,102,805

ALUMINUM PRODUCTION FROM ALLOY Filed April 18, 1960 3 Sheets-Sheet 3 INVENTOR. GEORG MEfiSNER ttorneys United States Patent Ofiice new Patented Sept. 3, 1953 3,102,805 ALUMINUM PRQDUCTIGN FRGM ALLOIY Georg Messner, Via Del Den 3, Milan, Italy Filed Apr. .18, 1960, Ser. No. 23,080 8 Claims. (Cl. 75-68) This invention relates to the production of aluminum and particularly, to the production of relatively pure aluminum by recovery from an aluminum alloy, in which form it may be made available during its production process.

Briefly described, the invention embodies the concepts of effecting a separation of aluminum from impurities by solution of the aluminum alloy in a medium in which the impurities are insoluble and, after the impurities have been removed, the separation of the purified aluminum from the medium in which it has been dissolved, thereby to produce aluminum in a relatively pure state.

It is known to treat aluminum alloys with mercury to form an amalgam in which the impurities are insoluble to enable the separation thereof, as by decantation, filtration or the like. For initiation of the reaction to form the amalgam, the aluminum alloy is first treated with mercury in vapor form, after which it is placed in an extractor, under positive pressure, wherein the aluminum alloy is brought into contact with hot mercury incountercurrent flow for solution. The aluminum is taken into solution while the undissolved residue containing impurities is separated. The purified aluminum can then be separated from the mercury by cooling and by removal of the mercury by distillation.

The process described is subject to a number of deficiencies and objections from the standpoint of procedure,

. cost, and safety. It has been found that the wetting out.

of the aluminum alloy with mercury vapor to accelerate the solution in mercury is efiective only if afterwards the mercury vapors are cooled and liquefied on the surface of the metal prior to contacting the aluminum alloy with the hot mercury liquids. This combination of steps adds materially to energy requirements for cooling on the one hand, and then heating for the following extraction step. It extends the number of steps in the recovery process and it requires the use of additional equipment and space. Aside from the economic and procedural differences, bringing mercury vapor into contact with hot aluminum alloy is fraught with dangers of explosive reactions.

Furthermore, the pretreatment operates only to wet the alloy without the extraction of the contained aluminum by mercury, making it necessary thereby to require long working time, cumbersome equipment, and large quantities of mercury. It is also necessary, in the extraction step, to make use of large heads of mercury, in the order of 40-45 meters, in order to enable the use of high temperatures in the order of 560 C. in the extractor, for which purpose the liquid alloy is conveyed in suitably insulated and heated pipes of tungsten. In the described process, large surface area is required in the heat exchangers, necessitating the use of large quantities of mercury which slows the separation process and raises problems of obstructions or plugging of the equipment.

It is an object of this invention to produce aluminum in a relatively pure state from alloys of aluminum by a method and means which is free of many, if not all, of the difliculties and objections heretofore described.

It is another object to provide a safe, efiicient, and economical method of producing aluminum byselective solvency, using mercury as the working medium.

These and other objects and advantages of this invention will hereinafter appear and .for purposes of illustration, but notof limitation, embodiments of the invention are shown in the accompanying drawings, in which- FIGURE 1 is a schematic flow diagram illustrating the practice of this invention;

FIGURE 2 is a schematic flow diagram similar to that of FIGURE 1, showing a modification in the practice of this invention;

. FIGURE 3 is a schematic sectional elevational view of a modification in a means for introducing aluminum alloy into the separation apparatus; and

FIGURE 4 is a schematic sectional elevational View of a particular extraction system.

As used hereinafter, the term mercury shall be in- V tended to include not only mercury but alloys of mer-" In accordance with the practice of this invention, the aluminum alloy is pretreated in a manner to be brought into contact with the liquid mercury for extraction while the alloy is in a liquid state. Best results are secured when the liquid alloy is finely divided, as by comminution or atomization, when brought into contact with the liquid mercury. This may be achieved when the liquid alloy is sprayed into the mercury, and preferably, when the aluminum alloy is sprayed in a manner directly to impinge on the mercury while the latter is being vigorously agitated. Still better results are secured if, inaddition to the alloy, the mercury is likewise atomized when contacted by the finely divided alloy, as by spraying one into the other. The pretreatment step for more rapid and complete solution of aluminum in mercury, without the intermediate cooling and heating steps of the known process, can be carried out at atmospheric pressure or positive pressures such that the temperatures may vary from about 358 C. to 530 C.

In the extraction step, the two components, namely, the aluminum alloy and the mercury, are processed in unidirectional flow. This offers a considerable advantage because unidirectional flow minimizes or prevents problems of obstruction or clogging of the equipment such as is experienced in the present countercurrent flow process. Extraction is carried out a temperature above 400 C. and, preferably, at a temperature of about 530 C., but any temperature in between and slightly beyond 530 C. can be employed. In practice, the amount of aluminum dissolved in the mercury will range from about 25% by weight and preferably about 2.5% by weight,

and the extraction step will usually be completed in less 7 than 5 minutes and more often from 23 minutes, but any amount of time can be employed, if desired.

The components which are insoluble or remain undissolved in the mercury or in the solution of aluminum in mercury, can be separated simply by decantation of other conventional separating means. However, a small pro portion of insoluble components may remain behind in the liquid phase, as in a finely divided state or a slightly dissolved state. I have found that a rapid and quantitative separation of the remainder can be achieved by reduction in the temperature of the mixture toslightly below the saturation temperature for the amount of aluminum dissolved in the mercury whereby a small proportion of the dissolved aluminum will be precipitated from solution to carry the other insoluble impurities out with it. Cooling to effect crystallization of less than by weight of the dissolved aluminum is desirable. This can be achieved by heat exchange but it is preferred to effect the desired temperature reduction by way of expansion of the aluminum-mercury liquid to a lower pressure. It is preferred to carry out the expansion step in combination with one or more sprayings of the mercuryaluminum liquid phase into a chamber at lower pressure,

and preferably in a chamber which is filled with mercury vapors to achieve control in the vaporization or flashing of the mercurydue to the pressure drop.

The aluminum, present as 'an amalgam in the remaining mercury-aluminum liquid phase, is obtained in a relatively pure state'by cooling to a temperature at which the dissolved aluminum becomes lnsoluble in the liquid mercury to cause solidification, as by crystallization of the aluminum. At atmospheric pressure, this will occur at a temperature below 360 C. but it is preferred to i make use of a crystallization temperature in the order of about 300 C.

As previously pointed out, the pretreatment of the alloy can be carried out at normal pressure or under positive pressure. When spraying under positive pressure, it is preferred to make use of an inert gas, such as argon, as the pressurizing medium. This. offers the advantage of avoiding the use of high liquid heads which would otherwise be necessary to achieve the desired temperature, as in the present process. Theliquid mercury should be brought to a cor-responding pressure prior to its admixture with the aluminum alloy. Instead, it is possible to pres intersect and thoroughly penetrate each other, thereby to enable very fine particles intimately to contact each other to accelerate solution and minimize aggregation. The liquid aluminum alloy and liquid mercury can be simultaneously introduced through separate inlets or through injection or mixing nozzles.

During the described pretreatment, it is possible to adjust the ratio of aluminum alloy to mercury and to adjust the initial temperature of the components, depending upon the ratio of solvent mercury to dissolved aluminum and the temperature of the extraction step. In

this way, heat accumulated in the liquid aluminum alloy can be utilized to heat the solvent mercury. If the amount of heat is insufficient, 'a complementary input of heat can be made.

I From the pretreatment zone, the aluminum alloy mixed with mercury is advanced to the extraction zone without intermediate cooling and heating steps. Consequently, the process embodying the features of this invention enable considerable savings in equipment, power, and mercury, as well as improving upon the safety of the process by comparison with the presently known process. The utilization of lesser amounts of mercury in the process of this invention has direct effect upon the ease of the final separation of the insoluble and undissolved particles. The extraction step with parallel currents or unidirectional flow can be effected in any known way. For example, the mixture of aluminum alloy and liquid mercury can be advanced through a horizontally disposed cylinder embodying a screw conveyer for concurrently blending and advancing the materials as will hereinafter be described. The extraction step can also be effected by the means illustrated in FIGURE 4. Such procedure, as will hereinafter be described, cancels subsidiary mechanical equipment and it enables control of the time of contact between the solid aluminum alloy particles and liquid mercury to minimize the extraction of aluminum by mercury in terms of the grain size of the particles, thereby to minimize or prevent the passage of undissolved aluminum into the next step of the process.

It is believed that invention exists in the extraction and separation steps independent of pretreatment such that concepts of this invention will also have application, in some cases, the conditions of which could be easily determined by one skilled in the art, directly to treat powdered aluminum alloy with mercury. However, it would be desirable to start with an aluminum alloy pretreated to render it easily soluble in mercury, such for example as by the present vapor treatment.

The liquid mercury-aluminum phase from which the insoluble components may or may not have been separated, is then introduced, as by spraying into an expansion chamber in which a pressure is maintained by mercury vapor. The mercury vapor pressure Withinthe chamber is maintained at a level below the pressure of the liquid whereby expansion of the aluminum-mercury liquid will result in partial vaporization of the atomized mercury-aluminum phase, with a corresponding slight drop in temperature to a level slightly below the saturation temperature of the aluminum in said phase. In the following crystallization of aluminum which takes place, other insoluble matter will be entrained to enable substantially complete removal of said insolubles which rise to the top to enable separation thereof as by means of 'a screw conveyer or other displacement or separating means, including filtration. As previously pointed out, the expansion can be carried out in one or in several separate steps. When more than one expansion step is employed, it is desirable to allow crystallization to take place after each such expansion step. With this method, it is possible to achieve the same rate of crystallization but with a lesser amount of aluminum separation by comparison with the single expansion step.

In practice, use can be made of a pressure drop of about one-half atmosphere or more which will prow'de for a corresponding temperature drop from about 10 C.

to about 50 C. The pressure drop can be varied but it .is preferred to calculate for a total temperature drop of between 20-50 C. so that not more than about 10% of the dissolved aluminum will be precipitated.

In order to avoid the difficulties arising from clogging, the conveyers should be arranged at a slope with the ends remote from the separating vessel at a lower level than the ends wherein separation is to be effected. it is an important concept of this invention to maintain the level of the mercury-aluminum phase in the bottom of the separation vessel at a level lower than thev junction points of said conveyers. This feature not only helps minimize clogging in the conveyers but it also permits rapid and easy decantation of the mercury-aluminum phase.

As another important concept, it will be found that the layer of solid material composed of crystallized aluminum and mercury insoluble substances which form I continuously in the separation vessel and are decanted out of the aluminum-mercury phase, will function as a After the removal of the mercury-insoluble substances or the undissolved material, the recovery step for the separation of relatively pure aluminum is achieved by cooling the liquid mercury-aluminum amalgam to a temperature at which the aluminum becomes substantially completely insoluble in the mercury. At operating presures,

the walls of the container.

this can be achieved by cooling to a temperature of 360 C. or less, and preferably to a temperature of about 300 C. or less. At such temperature, mercury will have a vapor pressure of about 249 mm. In the preferred practice, this can be achieved by expansion to bring about a drop in temperature to the desired level, as by spraying the liquid phase into an expansion chamber where the mercury vapor tension is such that a temperature drop to about 300 C. is achieved. The aluminum will c1ystallize as fine particles while the mercury will remain either in vapor or liquid form to enable substantially complete separation.

Instead, the desired temperature drop and crystallization can be achieved by injecting the amalgam into a suitably cooled liquid mercury. In such event, the amalgam should be injected into the interior of the body of colder mercury and in a direction away from the container walls to minimize caking of the aluminum crystals on The temperature control can be achieved by the ratio of hot amalgam to cold mercury, depending also upon the temperature of the amalgam and the cold mercury. The latter can be prepared in any known manner, as by the evaporation of a hydrocarbon introduced into the liquid mercury. Any hydrocarbon which might remain will be found to have no detrimental effects upon the recovery of aluminum even in the event that fusion should be employed as final steps in the separation.

The crystallized aluminum, which will usually retain a substantial amount of liquid mercury, will form in an upper layer over the free liquid mercury thereby to enable substantial separation of one layer from another, as by decantation. The solid aluminum particles can also be separated from liquid mercury by centrifuge or other solid-liquid separating means.

In a preferred embodiment of the invention, solid aluminum particles are separated from liquid mercury by squeezing the material between parallel foraminous belts traveling in the same direction for displacement of the solid aluminum concurrently with the separation thereof from liquid mercury. Prior to the separation step or as a part thereof, the mixture of aluminum crystals and liquid mercury can be subjected to a scrubbing action, using a component of liquid mercury, preferably in a purified state, as the scrubbing medium with a view towards replacing the mercury liquid originally present in the amalgam with the fresh increment of mercury, thereby to remove the liquid phase which might contain some dissolved impurities. This will free the mercury of the amalgam for purification or recovery of impurities to enable the liquid mercury to be recycled through the process, as will hereinafter be described.

I have found that the process forming the subject matter of this invention can be applied not only to the preparation of pure aluminum but also to the production of pure or concentrated metals which might be originally allied with aluminum. By varying the techniques of the described process, one can produce, for example, more or less pure or aluminum-free beryllium from an aluminum-beryllium alloy, or highly concentrated silicon, titanium, uranium, zirconium, manganese, vanadium, chromium, hafnium, niobium, tantalum, etc. might be obtained in a similar manner.

I have found that aluminum may be dissolved under considerably lower pressures if alloys of mercury are used instead of pure mercury. In such instance, suitable materials would comprise mercury containing a small peroentage by weight of potassium, sodium, zinc, tin or other metal easily dissolved in mercury.

It has been found, as previously stated, that the removal of an alkaline metal, zinc, tin and/or a similar metal, either from pure crystallized aluminum or from insoluble, previously separated substances, may be achieved by washing with pure mercury. This will hereafter be illustrated with reference to sodium.

Referring now to the drawings, FIGURE 1 shows a closed chamber 1 filled with argon under pressure. Mounted within the chamber 1 is a vessel 2 for receiving the aluminum alloy to be processed. A centrifugal pump 3 is arranged to deliver liquid mercury \to a mixing nozzle 4- into which aluminum alloy from the vessel 2 flows through passage 5. The outlet in the bottom wall of the vessel 2, for communication with the passage 5, is provided with a flow control valve 6 which may be adjusted by means of a control rod '7 to vary the quantity of aluminum alloy flowing from the vessel into the passage 5. The intake pipe to the pump 3 is indicated by the numeral 8. This passage is provided with a glass gauge 9 for visual control to maintain the mercury at a desired level, preferably a constant level, for regulating the pump. Beyond-the mixing nozzle 4 there is provided a cylinder 10 having a conveyer screw ll adapted to advance the circulation of the incoming mixture rot materials. Cylinder it} communicates at the far end with a separation vessel 12, the "upper portion of which is provided with a restricted throat 13 for communication with a sloping cylinder 14 having a conveyor screw 15, and the lower end of the vessel 12 communicates with a belt tube 16 leading into a separation vessel 17, hereinafter described. From cylinder M- a vertical pipe 18 represents a passage through which liquid mercury may ascend to another sloping cylinder 19 having :a screw 20 mounted for rotational movement therein. Cylinder .19 is surrounded by a heating jacket 21 having an outlet 22. at one end and an inlet 23 at the other. A condenser 24 is arranged in communication with the passage for return (of condensed mercury to the column 13.

The vessel 17 communicates at its upper end with a mercury condenser 25 which is suitably cooled. In the lower end portion of the vessel 17, a nozzle 26 is mounted for introduction :of the aluminum-mercury phase in an atomized state. When the mercury-aluminum mixture expands into the vessel 17, cooling will :occur and a small quantity of aluminum will be crystallized for separation as a solid, as indicated at 27, thus forming a layer which can operate as a filter for particles falling down by gravitational force within the vessel 17. Adjacent the bottom end of the vessel =17 and in crosswise alignment with the layer '27, the vessel is provided with an opening in communication with a sloping cylinder 28 having a screw conveyer 29 which extends into the vessel for displacement of a certain quantity of the solid particles together with some occluded mercury through the vertical pipe 30, in communication with the opposite end of the cylinder, to the sloping cylinder 31 arranged and equipped in a manner similar to the cylinder 19. The lower end portion of vessel 17 is in the form of a hopper, such as a conical vat 32 having an opening in the lower end in communication with a pipe 33 through which the liquid phase is conveyed to a nozzle 34 mounted within a crystallizer 35 having a condenser 36 in communication with its upper end for the condensation of mercury vapors. Upon atomization and expansion of the mercuryaluminu-m mixture upon release from the nozzle 34, a temperature drop to about 300 C. will be automatically effected, at which temperature the aluminum will be insoluble in the liquid mercury to cause crystallization thereof from solution. Crystallizer 35 is provided with an opening in its lower end for communication with a cylinder 37 having a screw conveyer 38 for advancement of the mixture of mercury and aluminum to an air-free box 39 maintained under normal pressure and in which the separation of mercury and solid aluminum takes place. A pair of endless conveyer s are arranged for travel in closely spaced-apart, parallel relation over rollers ll and between which the mercury-aluminum paste is advanced to a cylinder mill 42 while simultaneously compressing the paste there between to enhance separation. A bucket elevator 43 is provided within the cylinder mill 42 for raising the now-hardened aluminum amalgain to the inlet ofa melting turnace 44 which is provided at its upper end with a mercury condenser 45 and at its lower end with a liquid seal 46.

FIGURE Q illustrates a diiferent embodiment and arrangement of apparatus for carrying out the invention. The centrifugal pump of the previous arrangement is identified by the numeral 47 and the 'atomizing nozzles are identified by the numeral 48. A chamber 49 is filled with an inert gas such as argon at normal pressure. The vessel which supplies the aluminum alloy to the system is identified by the numeral '50 and the stopper by which flow is controlled is identified by the numeral 51. Piping 52 communicates the container 50 with the nozzle 53 in the chamber 49. The piping 54 communicates the outlet in the bottom side of the chamber 49 with the extraction cylinder 57, heat being introduced into the mixture by conventional means during passage through the piping 54, as :by means of an electrical current, the terminals of which are represented by the numeral-s 55 and 56 for resistance heating. The cylinder 57 is provided with a screw 58 for advancement of the mixture theretbrough.

A supply of inert gas, such as argon, is made available trom the chamber 59, preferably in the form of a rubber envelope which is connected by means of la mercury condenser 60 to the mixing chamber 49 in which normal argon pressure is maintained.

From the cylinder 57 the mixture is advanced into the atomizin-g chamber 61 connected at its upper end to a condenser 62. and at its bottom end to chamber 63. The latter constitutes a cooling chamber maintained at a temperature of about 300 C. by the introduction of mercluy at 50 C. through line 64.

The atomizing chamber 61 is provided with an outlet intended to be above the level of the liquid in the chamher, and the outlet communicates with a downwardly inclined cylinder 67 having a vertical riser 68 at its lower end portion. The riser communicates at its upper end with another sloping cylinder 69 fitted with a jacket for heat exchange.

The cooling chamber 63 is provided with an outlet in an intermediate portion thereof in communication with an inclined cylinder 65 provided with a screw conveyer for the advancement of solid materials rising to the surface of the liquid to 'a squeeze conveyer similar to that which is described in FIGURE 1 for the separation of the solidified aluminum from liquid mercury.

FIGURE 3 illustrates a further modification in a feeding and mixing device which may be used in the practice of this invention. In this construction, use is made of a pump 71 tor the advancement of liquid mercury to the chamber 70 provided with an injector communicating with the vessel 72 tor the supply of aluminum alloy through the passage 7 3. The mixture of aluminum alloy and mercury is advanced from the chamber 70 through steel piping 74 to one end of a cylinder 75 wherein solution between the mercury and aluminum is achieved.

FIGURE 4 illustrates a further embodiment in the extraction means. In this embodiment, the mixture of aluminum alloy and mercury from the pretreatment step isintroduced at a temperature of about 530 C. through passage 77 into a tank 78. The mixture is sprayed and dispersed by ejection from the nozzle 79 into the apex portion of the cone-shaped tank so as to be dispersed and impacted for violent movement in rebounding from the walls of the tank downwardly onto the bed of solid particles 80 formed, on the one hand, of aluminum which has not been dissolved and, on the other hand, by insoluble matters separated from the liquid mercuryaluminum phase. The latter collects as a bottom layer 81 which is led through passage 82 to the subsequent purification and recovery means.

' The mixture dispersed at 79 will first meet the coarser particles rising to the surface in the tank 78, after which it will come into contact with the finer particles such that solution of aluminum in mercury will be enhanced by the physical actions of abrasion and disintegration which would normally result. This process enables a systematic exhaustion of the aluminum alloy and minimizes the advancement of undissolved aluminum into the subsequent steps of the process.

Description will now be made of the practice of this invention with the apparatus described.

Example 1 Referring first to FIGURE 1, mother liquor at the rate of kg. per minute is recycled from the crystallization chamber 44 to the pump 3 wherein it is raised in pressure to about 15 atmospheres. From the pump 3, the liquid mercury, at a temperature of about 300-360 C., is introduced into the mixing nozzle 4. Simultaneously, liquid aluminum alloy formed of about 60% aluminum and 40% silicon and at a temperature of 960970 C. is introduced into the mixing chamber at a rate of about 5.8 kg.

per minute. The aluminum silicon alloy is supplied from the heated crucible 2 which is mounted within a chamber 1 pressurized to about 14 atmospheres with argon. The rate of flow of the aluminum silicon alloy is controlled by the stopper 6 to provide for a mixture maintained at a temperature of about 530 C. in the mixing chamber 4.

The mixture 'of liquid mercury and aluminum alloy flows at a temperature of about 530 C. from the chamber 4 to the extractor 12 by way of the screw conveyer and blender 10. The material is under a pressure of about 12 atmospheres and after a few minutes in the thermal insulated solubilizer and conveyer 10, the major part of the aluminum of the alloy will become dissolved in the liquid mercury to form an amalgam. In the housing 12 the mixture separates whereby undissolved material rises to the surface of the mercury-aluminum phase to enable removal by the displacement means 14 for introduction into the riser 18 having a head sufficient to maintain the desired pressure conditions. The elevated mercury surface is situated in the inclined cylinder 19 fitted with a conveyer screw 20 which operates to skin the residue from the surface of the mercury raised to elevated temperature by the heated jacket 21. Any mercury which is vaporized is condensed in the condenser 24 for return to the mercury surface in a liquid state.

The dissolved mercury-aluminum phase, together with the finely divided residues which might remain therein, flows from the separator 12 to the spray nozzle 26 in the chamber 17 whereby the amalgam is introduced intothe chamber with expansion to a pressure of about 6 .5 atmospheres which is maintained in the vessel by the suitably cooled mercury vapor condenser 25. Upon expansion, the temperature of the material introduced into the chamber 17 will be reduced to a temperature of about 495 C.,

which is below the saturation point of aluminum in the mercury. Thus, a small quantity of aluminum will precipitate and will operate to collect the remaining particles of residue in the system. The solids will form as a layer 27 above the mercury-aluminum phase to act as a filter for the mercury-aluminum liquid passing therethrou-gh' to achieve more complete separation of any solids which might be entrained with the liquid. The solids are displaced from the chamber 17 by the screw conveyer 29 to the riser 30 wherein they are brought up to the mercury level in a continuous stream while the purified mercuryaluminum phase filters through the fluid bed of solid 'par ticles 27 for passage to the main aluminum crystallization step.

Crystallization for separation of the purified aluminum from the liquid mercury is effected by expansion upon spraying through a nozzle 34 into the crystallizer 35 maintained by mercury vapor at a pressure of about 245 mm. of mercury. Upon expansion, a temperature drop to about 300 C. or less is established, at which temperature the aluminum becomes insoluble in the mercury, ex cept for a few tenths of a percent, to cause separation thereof by crystallization.

The mixture of aluminumcrystals and liquid mercury is displaced from the crystallizer 35 by means of the screw conveyer 38 into the air-free box 39, under normal pressure. Separation of solid aluminum from liquid mercury will automatically occur within this chamber whereby the liquid mercury can be returned by way of passage 3 to the centrifugal pump 3 as recycle, while the paste of aluminum crystals and retained liquid mercury in the amount of about 90% mercury and 10% aluminum is displaced between the flights of the foraminous conveyer belts 40 Where additional mercury is pressed from the mixture, as by means of the rollers 41.

The friableproduct from the press, containing about 20% aluminum, is charged to the roller mill ll wherein the aluminum content is raised to about 60-65%. From this point, the solid material is raised by a bucket elevator 43 to a melting furnace 44 wherein the very hard aluminum amalgam is heated to a temperature of 700750 C. The mercury is removed by distillation with a stream of argon under normal pressure and the vapors are condensed in the condenser 45 for recycling through passage 8 into the system. Liquid aluminum, freed from the merciu'y, will collect in the bottom of the furnace and can be tapped therefrom through the liquid seal 46. The product will be found to contain 99.99% aluminum.

Example 2 The following example is made with reference to the flow diagram as set forth in FIGURE 2 of the drawing.

Liquid mercury at about 290 C. is caused toflow at a rate of 175 kg. per minute from the centrifugal pump 47 to the atomizing nozzle 48 into the chamber 49 maintained under an inert condition by argon at normal pressure. Simultaneously, liquid aluminum alloy at a temperature of about 700 C. is caused to flow at a rate of 3.8 kg. per minute from the melting crucible 50 to the atomizing nozzle 53 under the pressure of the column of the liquid metal 52. The liquid aluminum is introduced in a manner such that the dispersion cone of mercury intersects the dispersion cone of the aluminum alloy containing about 95% aluminum, with'the remainder composed of copper, iron, silicon, tin, zinc and other residual metals. The column 52 is about 8 mm. high, and the bolttom of the chamber 49 is about 12 meters above the dissolver 57 to which the mixture of aluminum alloy and liquid mercury is advanced through the passage 54. The atomizing chamber 49 is in communication with the resilient bag 59 having a capacity of about cubic meters and half filled with argon to maintain constant atmospheric pressure and wherein the bag functions as a cushion to compensate for any contractions or expansions of the gas 1n the atomizing chamber.

The Water-cooled mercury vapor condenser 60 interposed between the chamber 49 and the bag 59 minimizes the entrance of hot mercury vapors into the bag.

The solidified fine particles of aluminum alloy wetted with mercury at about 360 C. travels through the passage 54 to the dissolver 57 and it is heated during such passage from 360 C. to 530 C., as by the electrical resistance means 55 and 56. The heated mixture is displaced through the dissolver 57 by the screw 58 to the atomizing chamber 61 ,Where it is sprayed through the nozzle into the atomizing chamber at a pressure of 6.5 atmospheres. Upon expansion, the mixture cools to a temperature of about 495 C. for crystallization of an amount of aluminum corresponding to or less of the aluminum in the system, as previously described in connection with FIG- URE l.

The bed of solid particles collected on the surface is continuously displaced by the screw conveyer 67 to the riser 68, as previously described, While the dissolved mercuryaluminum phase filters through the layer to achieve more complete separation of the solids, and from the chamber 61 the aluminum-mercury amalgam flows into the cooling chamber 63 wherein it is introduced into the iii center away from the Walls into a mass of cooler mercury at about 300 C. The temperature of 300 C. in the cooled mercury chamber is maintained by the continuous introduction of about kg. per minute of mercury at a temperature of 50 C. through passage 64. At this temperature, all but a fraction of 1% of the aluminum is crystallized for separation from the mercury. The valve in vessel 63 is controlled in a manner such that the level of liquid mercury in the conical portion of the vessel 61 will remain relatively constant and at a level lower than the inlet of separator 67.

The crystallized aluminum is skinned from the surface of the mercury in vessel 63 by the screw conveyer 65 for displacement into the air-free box of the type described in the previous example. The major part of the mercury phase from the crystallization of aluminum is automatically recycled from the vessel 63 to the centrifugal pump 47, while an amount corresponding to about 140 kg. per minute is branched off through passage 66 for coo-ling to 50 C. as a recycle through passage 64. The desired cooling may be achieved by heat exchange or by the introduction of a liquid hydrocarbon having a boiling point at about 50 C. In a secondary circuit 64-6t:, lead, tin, zinc and other residual metals can be continuously separated by cooling pant of the liquid flowing in the circuit, or by other known means.

The pure liquid aluminum of 99.99% aluminum can be further refined to 99.999% if the mercury-aluminum phase is submitted to acornplementary rare-crystallization step wherein dissolved copper is removed. The entire equipment described is adapted to be thermally insulated.

Example 3 Mercury liquor recycled from the extractor at about 290 C. is raised to about 20 atmospheres pressure by the centrifugal pump 71 (FIGURE 3) and charged into the outer section of the injection-type mixer 70. Simultaneously, liquid aluminum alloy, containing about 60% aluminum and 40% silicon, is circulated at a rate of about 5.8 kg. per minute from the crucible 72 through the tungsten piping 73 to the mixing nozzle '70 at a temperature of about 900970 C. The pressure within the chamber is maintained at about 12 atmospheres and the mixture provides fora temperature of about 530 C. From the mixer, the materials continue under the pressure through the passage 74 to the dissolver or blender 75. From this point on, the solution of aluminum in mercury and the separation of the solids and impurities therefrom is achieved as previously described in thermally insulated equipment.

Example 4 Liquid mercury at about 290 centrifugal pump 47 (FIGURE rate of about kg. per minute While liquid. aluminum alloy, containing 90% aluminum and 10% beryllium at 111 C., is advanced from the crucible 50 through the passage 52 to the mixer at a rate of 3.7 kg. per minute. From the mixing chamber 49, inerted with argon vapor, the mixture is advanced through passage 56 to the dissolver 57 while being progressively heated from about 300 C. to 530 C. The materials are retained at the elevated temperature in the dissolver for about 1% times that set forth in Example 2 to achieve a substantially complete solution of the aluminum. By the pie-crystallization of a fractional amount of the aluminum in the vessel 61, undissolved particles of beryllium are precipitated to enable removal by the screw conveyor 67, as previously described. For scrubbing the beryllium, mercury at about 350 C. is introduced from the top of the riser 68 for countercurrent fio-W. The beryllium powder rises to the surface of the mercury in the sloping cylinder 69 and is separated from the major part of the adhering mercury by heating to a temperature of about 450 C. by means of the jacket. In a second heating zone, free of air, mercury-free beryllium is obtained which contains but a small C. is advanced from the 2) to the mixer 49 at a proportion of aluminum. The mercury-aluminum phase separated from the undissolved residue in this pre crystallization step is thereafter advanced to the principal crystallization vessel 63. crystallized aluminum is carried oif by the sloping conveyer 65 while the condensate of mercury is recycled through passage 76 for use as a scrubbing liquid to purify the aluminum crystals in countercurrent flow through the separator.

Example 5 Sodium mercury alloy containing about sodium is advanced in aliquefied state at about 400 C. and at a rate of about 180 kg. per minute into the outer section of a mixing injector, as by means of a centrifugal pump 47. Simultaneously, liquid aluminum alloy, containing 60% aluminum and 40% silicon at about 960-970 C. is advanced from a melting crucible 50, positioned about 4 meters above the mixing nozzle, through the passage 52 to the central portion of the mixing chamber. The resulting mixture is advanced to the dissolving conveyer at about 520 C. wherein it is retained for about 5 minutes to maximize the solution of aluminum in the mercury alloy. The charge is then submitted to a pro-crystallization, as in chambers 61 (FIGURE 2) or 17 (FIG- U-RE 1), at a temperature of about 490 C. whereby 10% or less of the dissolved aluminum is precipitated from solution, thereby to effect more complete removal of entrained impurities, including finely divided silicon, in the aluminum-mercury alloy amalgam. Thereafter, the purified solution of aluminum in mercury alloy is advanced to the principal crystallization chamber and reduced to a temperature of about 350 C. for substantially complete separation of the entire increment of aluminum. Such reduction in temperature can be achieved either by temperature drop, as in Example 1, or by the injection of cold mercury, as in Example 2.

During the principal crystallization to separate purified aluminum at a temperature of 350 C. or less, the precipitatedaluminum is washed for the purpose of removing any sodium-bearing liquor, as by the passage of purified mercury at a temperature of 350 C. in countercurrent flow therewith, using apparatus such as shown at 63 in FIGURE 2. In the foregoing example, it is unnecessary to make use of large mercury heads for generation of pressure since pressures in excess of 2 atmospheres will prevail possibly only in the hottest parts of the system.

It will be apparent from the foregoing that I have provided a simple and efiicient means relying upon the principle of selective solvency for the purification of aluminum in a continuous system, whereby aluminum is separated from alloys of the type formed during the beneficiation process or other impurities which might be found with the aluminum.

This application is a contirruationiu-part of my copending application Serial No. 667,218, filed June 21, 1957, now abandoned.

It will be understood that the times, temperatures and pressure conditions set forth in the process may be varied and that the construction and arrangement of equipment and their operations may also be varied without departing from the spirit of the invention, especially as defined in the following claims.

1 claim:

1. A continuous method for the purification of aluminum by separation from other elements in combination therewith comprising the steps of mixing the impure aluminum with mercury at an elevated temperature for solution of aluminum in the mercury by spraying a fine dispersion of liquid aluminum into intimate contact with a fine dispersion of liquid mercury, maintaining the mixture in undirectional flow for a time and temperature sufficient to dissolve a substantial proportion of the aluminum in the mercury, separating the solids which remain undissolved in the solution of aluminum and mercury by cooling the temperature to a temperature slightly below the saturation temperature for the amount of aluminum dissolved in mercury to precipitate a small proportion of the aluminum dissolved in the mercury and thereafter transferring the mixture to a chamber and separating the dissolved aluminum from the liquid mercury in the purified liquid aluminum-mercury phase by reducing thepurified liquid aluminum-mercury phase to a temperature below. the temperature at which aluminum is soluble in mercury in substantial amounts to solidify the aluminum from liquid mercury.

2. A continuous process for the purification of aluminum by separation from other elements in combination therewith, which comprises the steps of mixing liquid aluminum alloy with liquid mercury at temperatures of substantially from 358 to 530 C.; maintaining the mixture for approximately 2-5 minutes at a temperatureof 400 to 538 C. while in unidirectional flow thereby dissolving aluminum in liquid mercury by extraction from said alloy; cooling the solution of aluminum in mercury to a temperature ranging from 300 to below 360 C. thereby causing the aluminum to solidify; and separating the solidified aluminum.

3. A continuous process for the purification of aluminum by separation from other elements in combination therewith, the steps which comprise spraying finely divided liquid aluminum alloy into liquid mercury under pressure at temperatures of substantially 358 to 530 C.; maintaining the mixture for approximately 2 to 5 minutes at a temperature of 400 to 538 C. while in a unidirectional flow thereby dissolving aluminum in liquid mercury by extraction from said alloy; cooling the solution of aluminum in mercury to a temperature ranging from 300 to below 360 C. thereby causing the aluminum to solidify; and separating the solidified aluminum.

, 4. A continuous process for the purification of aluminum by separation from other elements in combination therewith, the steps which comprise contacting 2 to 5 parts by weight finely divided liquid aluminum alloy with parts by weight finely divided liquid mercury by spraying one into the other at temperatures of substantially 358 to 530 C.; maintaining the mixture for approximately 2 to 5 minutes at a temperature of 400 to 538 C. while in a unidirectional flow thereby dissolving aluminum in liquid mercury by extraction from said alloy; cooling the solution of aluminum in liquid mercury to a temperature ranging from 300 to below 360 C. thereby causing thealuminurn to solidify; and separating the solidified aluminum.

5. -A continuous process for the purification of aluminum by separation from other elements in combination therewith, the steps which comprise mixing 2 to 5 parts by weight liquid aluminum alloy with 100 parts by weight liquid mercury at temperatures of substantially 358 to 530 C.; maintaining the mixture for approximately 2 to 5 minutes at a temperature of 400 to 530 C. while in a unidirectional flow thereby dissolving aluminum in liquid mercury by extraction from said alloy; cooling the solution of aluminum in mercury, by introducing cold mercury therein, to a temperature ranging from 300 to below 360 C. thereby causing aluminum to solidify; and separating the solidified aluminum.

6. A continous process for the purification of aluminum by separation from other elements in combination therewith, the steps which comprise spraying finely divided liquid aluminum alloy under pressure into liquid mercury at temperatures of substantially 35 8 to 530 C.; maintaining the mixture for approximately 2 to 5 minutes at a temperature of 400 to 530 C. while in a unidirectional flow thereby dissolving aluminum in liquid mercury by extraction from said alloy; cooling the solution of aluminum in tmercury, by introducing cold mercury therein, to a temperature ranging from 300 to below 360 C.

13 thereby causing the aluminum to solidify; and separating the solidified aluminum.

7. A continuous process for the purification of aluminum by separation from other elements in combination therewith, the steps which comprise spraying 2 to 5 parts by Weight finely divided liquid aluminum alloy into 100 parts by weight liquid mercury at temperatures of substantially 358 to 530 C.; maintaining the mixture under a pressure ranging [from atmospheric to substantially 12 atmospheres for approximately 2 to 5 minutes at a temperature of 400 to 550 C. while in a unidirectional flow thereby extracting aluminum from said alloy; cooling the solution of aluminum in a mercury to a temperature ranging from 300 to 360 C. thereby causing the aluminum to solidify; and separating the solidified aluminum.

8. The process as defined in claim 7, wherein cooling of said solution of aluminum in mercury is carried out by introducing cold mercury therein.

1 4 References Cited in the file of this patent UNITED STATES PATENTS 1,194,829 Fay Aug. 15, 1916 2,032,215 Kemmer Feb. 25, 1936 2,198,673 Loevenstein Apr. 30, 1940 2,207,461 Kemp July 9, 1940 2,434,775 Sosnick Jan. 20, 1948 2,676,358 Messner Apr. 27, 1954 2,707,678 Messner May 3, 1955 FOREIGN PATENTS 671,054 Great Britain Apr. 30, 1952 OTHER REFERENCES Chemical Engineers Handbook, 3rd ed., McGraw-Hill Book Co., Inc., NewYork, 1950, page 1676 relied upon.

Constitution of Binary Alloys, M. Hansen, McGraw- Hill, New York, 1958, pp. 99-100 relied upon showing the Al-Hg phase diagram. 

1. A CONTINUOUS METHOD FOR THE PURIFICATION OF ALUMINUM BY SEPRATING FROM OTHER ELEMENTS IN COMBINATION THEREWITH COMPRISING THE STEPS OF MIXING THE IMPURE ALUMINUM WITH MERCURY AT AN ELVEATED TEMPERATURE FOR SOLUTION OF ALUMINUMM IN THE MERCURY BY SPRYAING A FINE DISPERSION OF LIQUID ALUMINUM INTO INTIMATE CONTACT WITH A FINE DISPERSION OF LIQUID MERCURY, MAINTAINING THE MIXTURE IN UNDIRECTIONAL FLOW FOR A TIME AND TEMPERATUE SUFFICIENT TO DISSOLVE A SUBSTANTIAL PROPORTION OF THE ALUMINUM IN THE MERCURY, SEPARATING THE SOLIDS WHICH REMAIN UNDISSOLVED IN THE SOLUTION OF ALUMINUM AND MERCURY BY COOLING THE TEMPERATURE TO A TEMPERATURE SLIGHTLY BELOW THE SATURATION TEMPERATUE FOR THE AMOUNT OF ALUMINUM DISSOLVED IN MERCURY TO PRECIPITATE A SMALL PROPORTION OF THE ALUMINUM, DISSOLVED IN THE MERCURY AND THEREAFTER TRANSFERRING THE MIXTURE TO A CHAMBER AND SEP- 